Shrimp Shells Make Compostable, Moldable Bioplastic

A low-cost, biodegradable plastic made from shrimp shells could be used in mass production of a wide variety of consumer goods. The material is v2.0 of the stuff we told you about a couple years ago called Shrilk, which combined chitin from shrimp shells with a protein derived from silk. This time, the Harvard Wyss Institute researchers dropped the silk and kept the chitin.

The bioplastic is an engineered chitosan, derived from chitin originating in discarded shrimp shells. Chitin, a long-chain polysaccharide polymer, is what gives rigidity and toughness to the exoskeleton of insects and the hard shells of crustaceans like shrimp. It also makes insect wings both strong and flexible, and it's available in huge quantities. But until now, making complex, 3D shapes with this material hasn't been possible.

Wyss Institute researchers have created a low-cost, biodegradable plastic made from shrimp shells that can be used to mass-produce 3D compostable consumer goods using injection molding or casting processes. To demonstrate this, they molded a series of chess pieces made of their chitosan bioplastic. (Source: Harvard's Wyss Institute)

The Wyss Institute researchers who invented the original Shrilk and developed this second iteration are Javier G. Fernandez, PhD, a postdoctoral fellow at the institute, and Donald Ingber, MD, PhD, the institute's founding director. They describe their work in an article in Macromolecular Materials & Engineering (purchase or subscription).

The new chitosan bioplastic material is entirely biodegradable. It breaks down completely within about two weeks after being discarded in the environment, and even releases nutrients during its breakdown that plants can use. To demonstrate this ability, the research team grew a California black-eyed pea plant in soil they'd enriched with the chitosan polymer.

Combining the desired structural properties with biodegradability was not an easy task. To make their new chitosan bioplastic material even less expensive and easier to fabricate, the researchers dropped the silk component from the original mix. They also developed a way to process it so it can be used to mass-produce 3D objects -- such as food containers, toys, and cell phones -- in conventional injection molding or casting manufacturing processes. The key to this breakthrough was how the material is fabricated at the molecular level.

The research team observed that different processing methods, including factors such as concentration and temperature, led to differences in the mechanical properties and molecular arrangement of the new chitosan polymer. Some formulations resulted in an undesirable brittle and opaque material, while others yielded flexible and tough material, which was the goal. Analyzing those differences, the researchers developed a scalable manufacturing method that would let them commercially produce large, complex 3D shapes made of the chitosan bioplastic. The material's formulation can also be modified so it can be used in water. Next steps include refining the fabrication methods to transfer the technology to commercial manufacturing, and finding an industrial partner.

Yes, apparently chitosan is becoming quite popular as the basis for bio plastics, so my research shows. It's chitosan, not the material from the Harvard researchers. Story should post soon so you can check it out!

Liz, thank for posting that. It's good to know others are working on this material. Did you mean working on a different form of chitosan, or working with this actual chitosan-derived material from the Harvard Wyss project?

I just went back to this story for context as I've found a new group of researchers in Spain Basque country working on the use of this material as an alternative to plastic. It's proving to be a good foundation for more eco-friendly "plastics."

Chitin and Chitosan can be used in many industries, not only for plastics.

Chitin is the base from where Glucosamine is obtained. Pharmaceuticals.

Chitin in powder can be used in treatment of some types of skin burns.

Chitosan can be used in agriculture, in many types of crops, and Papaya, Sugar Cain, Tangerine, Grapes, Tomatoes, and many others.

Also Chitosan is being used in medicine, and by the USA Armed forces supplying their members in the field of action with packs of bandages, to stop bleeding from wounds. These bandages are impregnated with Chitosan, to seal the wound. In addition given the antibacterial action of the Chitosan, keeps the wound free of infection. Understand they are recently coming to the market in OVC sales.

Don´t know in USA, but in Europe, bed sheets on the hospitals are being impregnated or specially treated with Chitosan. These way patients with long stay in bed do not develop scars, plus no infection, do to bed bugs, or other invasive insects found in mattresses and bed linen.

There are so many more uses for these two natural bio-polymers, water treatment, wine industry, clothes, food industry, cosmetics (Chitosan helps the skin cells to keep healthy).

And as many of you mentioned, it is obtained from waist of crustacean.

Ann, Ok, now I am aware of what part of the shrimp contains the chitlin. I don't discard that part, it adds a nice texture to the shrimp.But I do discrd the heads and legs portion, which don't taste good at all. But the cat loves them anyways.

William, I'm not sure what you're asking. The material we describe here is made of chitosan, a form of chitin from discarded shrimp shells, which does not come from other shrimp parts. "Discarded" implies that commercial shrimp fishers would not be the source of volumes, but commercial food packers might be. Chitin is described by the Harvard researchers as being the second most abundant organic material on the planet (probably because of the huge mass of insect exoskeletons made of it), and shrimp are consumed in huge volumes by humans.

Those are both good points, William K., the commercial shrimp industry--which already does the "stinky" job--would certainly be a big factor in making the material available. And it's true that humans don't eat other parts that animals would. I guess it would depend on if the material used for bioplastic is available in those parts as well.

My guess is that to have enough of the material to be economically viable the source would need to be commercial shrimp processors, which would probably simplify the transport logistics quite a bit.

I do wonder about how much of the rest of the shrimp is able to be included, since the food part of a shrimp is a bit less than half of the raw weight. I know that some animals will eat the whole shrimp, but I have no idea about what portion of the part that humans don't like is actually useable in the process. That would be sort of interesting to find out, what portion of the non-eaten shrimp actually works as feedstock for the recovery for the transformation process..

Good point, William K. shrimp shells are pretty stinky. I don't envy the person whose job it is to gather them for the transformation into biomaterial. Maybe if they are stored at the right temperature before use it won't be so bad.

University of Southampton researchers have come up with a way to 3D print transparent optical fibers like those used in fiber-optic telecommunications cables, potentially boosting frequency and reducing loss.

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